POST-GLACIAL ANALYSIS OF HARRINGTON LAKE, MAINE USING SEISMIC REFLECTION AND LIDAR DATA

The Mt. Kathadin region of Maine is a critical location in understanding deglaciation after the last glacial maximum. In central Maine, the topographic transition from the Penobscot Lowland into the upland area is interpreted as the northwestern boundary of marine strata during the Pleistocene. There are many lakes in the area, but stratigraphy within the lakes is poorly understood. For this study, we use CHIRP seismic reflection data to interpret and map seismic facies within Harrington Lake, ME. These data are compared to data from lakes farther to the south to reconstruct the last deglaciation. Whereas all lakes have thin, horizontal sedimentation, Harrington features an esker and thicker sedimentary packages than lakes 30-80 km southeast.

Harrington Lake lies northwest of the Penobscot Lowland, is bounded by a steep cliff at the southeastern corner and drains to the northwest. An esker enters the lake in the southeast, bifurcating in the north, continuing through the lake, and exiting in the northwest corner. Five seismic packages are observed in the lake from the CHIRP data. The basal layer has high reflectivity in the seismic data. The next two layers range up to 10 meters thick and are characterized by low reflectivity in the data. These layers are constrained to relatively deep basins which parallel eskers. The uppermost units range up to 8 meters thick and are characterized by thin horizontal layering and high reflectivity. Based on these observations we interpret the two layers overlying the bedrock as coarse grained sediment deposited by the esker. The thin layering in the two uppermost layers suggests a yearly fluctuation in meltwater supply. The lake likely experienced periods of high meltwater supply in the summer and low meltwater supply in the winter. These depositional environments create coarse and fine bedding, respectively.

Harrington Lake is interpreted to have experienced sediment deposition during deglaciation. The variation in seismic facies characteristics indicates the meltwater supply varied through time. Additionally, the presence of the esker within the lake provided both an internal sediment source and bathymetry that helped focus sediment accumulation. Eskers and distance from marine environments resulted in a high resolution and thick sedimentary record.